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-rw-r--r--src/shared/clock-util.c167
1 files changed, 167 insertions, 0 deletions
diff --git a/src/shared/clock-util.c b/src/shared/clock-util.c
new file mode 100644
index 0000000..a4c00d7
--- /dev/null
+++ b/src/shared/clock-util.c
@@ -0,0 +1,167 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <time.h>
+#include <linux/rtc.h>
+#include <stdio.h>
+#include <sys/ioctl.h>
+#include <sys/time.h>
+
+#include "alloc-util.h"
+#include "clock-util.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "macro.h"
+#include "string-util.h"
+
+int clock_get_hwclock(struct tm *tm) {
+ _cleanup_close_ int fd = -1;
+
+ assert(tm);
+
+ fd = open("/dev/rtc", O_RDONLY|O_CLOEXEC);
+ if (fd < 0)
+ return -errno;
+
+ /* This leaves the timezone fields of struct tm
+ * uninitialized! */
+ if (ioctl(fd, RTC_RD_TIME, tm) < 0)
+ return -errno;
+
+ /* We don't know daylight saving, so we reset this in order not
+ * to confuse mktime(). */
+ tm->tm_isdst = -1;
+
+ return 0;
+}
+
+int clock_set_hwclock(const struct tm *tm) {
+ _cleanup_close_ int fd = -1;
+
+ assert(tm);
+
+ fd = open("/dev/rtc", O_RDONLY|O_CLOEXEC);
+ if (fd < 0)
+ return -errno;
+
+ return RET_NERRNO(ioctl(fd, RTC_SET_TIME, tm));
+}
+
+int clock_is_localtime(const char* adjtime_path) {
+ _cleanup_fclose_ FILE *f = NULL;
+ int r;
+
+ if (!adjtime_path)
+ adjtime_path = "/etc/adjtime";
+
+ /*
+ * The third line of adjtime is "UTC" or "LOCAL" or nothing.
+ * # /etc/adjtime
+ * 0.0 0 0
+ * 0
+ * UTC
+ */
+ f = fopen(adjtime_path, "re");
+ if (f) {
+ _cleanup_free_ char *line = NULL;
+ unsigned i;
+
+ for (i = 0; i < 2; i++) { /* skip the first two lines */
+ r = read_line(f, LONG_LINE_MAX, NULL);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ return false; /* less than three lines → default to UTC */
+ }
+
+ r = read_line(f, LONG_LINE_MAX, &line);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ return false; /* less than three lines → default to UTC */
+
+ return streq(line, "LOCAL");
+
+ } else if (errno != ENOENT)
+ return -errno;
+
+ /* adjtime not present → default to UTC */
+ return false;
+}
+
+int clock_set_timezone(int *ret_minutesdelta) {
+ struct timespec ts;
+ struct tm tm;
+ int minutesdelta;
+ struct timezone tz;
+
+ assert_se(clock_gettime(CLOCK_REALTIME, &ts) == 0);
+ assert_se(localtime_r(&ts.tv_sec, &tm));
+ minutesdelta = tm.tm_gmtoff / 60;
+
+ tz = (struct timezone) {
+ .tz_minuteswest = -minutesdelta,
+ .tz_dsttime = 0, /* DST_NONE */
+ };
+
+ /* If the RTC does not run in UTC but in local time, the very first call to settimeofday() will set
+ * the kernel's timezone and will warp the system clock, so that it runs in UTC instead of the local
+ * time we have read from the RTC. */
+ if (settimeofday(NULL, &tz) < 0)
+ return -errno;
+
+ if (ret_minutesdelta)
+ *ret_minutesdelta = minutesdelta;
+
+ return 0;
+}
+
+int clock_reset_timewarp(void) {
+ static const struct timezone tz = {
+ .tz_minuteswest = 0,
+ .tz_dsttime = 0, /* DST_NONE */
+ };
+
+ /* The very first call to settimeofday() does time warp magic. Do a dummy call here, so the time
+ * warping is sealed and all later calls behave as expected. */
+ return RET_NERRNO(settimeofday(NULL, &tz));
+}
+
+#define EPOCH_FILE "/usr/lib/clock-epoch"
+
+int clock_apply_epoch(ClockChangeDirection *ret_attempted_change) {
+ usec_t epoch_usec, now_usec;
+ struct stat st;
+
+ /* NB: we update *ret_attempted_change in *all* cases, both
+ * on success and failure, to indicate what we intended to do! */
+
+ assert(ret_attempted_change);
+
+ if (stat(EPOCH_FILE, &st) < 0) {
+ if (errno != ENOENT)
+ log_warning_errno(errno, "Cannot stat " EPOCH_FILE ": %m");
+
+ epoch_usec = (usec_t) TIME_EPOCH * USEC_PER_SEC;
+ } else
+ epoch_usec = timespec_load(&st.st_mtim);
+
+ now_usec = now(CLOCK_REALTIME);
+ if (now_usec < epoch_usec)
+ *ret_attempted_change = CLOCK_CHANGE_FORWARD;
+ else if (CLOCK_VALID_RANGE_USEC_MAX > 0 && now_usec > usec_add(epoch_usec, CLOCK_VALID_RANGE_USEC_MAX))
+ *ret_attempted_change = CLOCK_CHANGE_BACKWARD;
+ else {
+ *ret_attempted_change = CLOCK_CHANGE_NOOP;
+ return 0;
+ }
+
+ if (clock_settime(CLOCK_REALTIME, TIMESPEC_STORE(epoch_usec)) < 0)
+ return -errno;
+
+ return 1;
+}